A light beam heating apparatus which heats up a local spot without touching thereat is widely used for soldering a small size electronic part. Wire solder or cream solder is used in general when the light beam heating apparatus is employed. A conventional feeder of wire solder employed in a soldering machine is described hereinafter by referring to FIG. 3.
In FIG. 3, a solder detector 2 monitors whether wire solder 1 is guided normally to a feeding roller 3 without interruption. Two feeding rollers 3 are driven by a motor 5. A feeding controller 6 controls a rotation of the motor 5. A distance between the feeding rollers 3 is adjusted responsive to a diameter of the wire solder. An abnormal halt detector 4 of the wire solder detects an abnormal halt of the wire solder at a downward place from the abnormal halt detector 4 due to e.g., a clogging in a feeding tube 7. When the abnormal halt detector 4 detects the halt of feeding the wire solder 1, the feeding controller 6 stops the motor 5 and prevents the wire solder 1 from being bent or deformed.
The feeding tube 7 has a dual structure, i.e., it comprises an outer tube and an inner tube. The wire solder 1 goes through the inner tube. The interior of the inner tube employs a material of a small slide resistance. A feeding direction fine adjuster 8 disposed at the tip of the feeding tube 7 can fine adjust a feeding direction of the wire solder 1.
In this feeder, the wire solder 1 has been guided to the feeding roller 3 via the solder detector 2. The two feeding rollers 3 feed the wire solder 1 to an objective spot by passing through the abnormal halt detector 4, the feeding tube 7, and being directed by the feeding direction fine adjuster 8.
The structure of the abnormal halt detector 4 is described by referring to FIG. 4. A guide tube 9 transfers the wire solder 1 into the abnormal halt detector 4 in which a spring 10 is incorporated. A dog 11 triggers a micro-switch 11.
When the wire solder 1 is blocked e.g. by a clog in the feeding tube 7, which is placed downward from the abnormal halt detector 4, feeding force from the feeding rollers 2 generates compression stress to the wire solder 1. When this compression stress excesses the stress which can compress and deform a spring 10, the dog 11 moves along the feeding direction of the wire solder 1 and touches an actuator 12b of a micro-switch 12 to actuate the micro-switch 12. When the micro-switch 12 is actuated, the feeding controller 6 stops the motor 5, and the feeding of the wire solder 1 by the feeding rollers 3 is halted, whereby the wire solder 1 is prevented from being bent and deformed. In other words, the abnormal halt detector 4 functions as a force sensor which senses a compression stress from the compressed and deformed spring 10. The compression stress is generated by the abnormal halt of the wire solder 1 and applied to the wire solder.
However, when the wire solder 1 has a so small diameter that stiffness of the wire is not enough, the compression stress applied to the wire solder 1 sometimes bends and deforms the wire solder 1 before compressing and deforming the spring 10. In other words, when the wire solder 1 having a small diameter and insufficient stiffness is employed, the wire solder 1 is not always prevented from being bent and deformed.